1. Field of the Invention
The invention generally relates to a bonding structure, and more particularly, to a bonding structure suitable to be electrically connected to an external circuit.
2. Description of Related Art
FIG. 4 is a top view illustrating a conventional bonding structure. Referring to FIG. 4, a conventional bonding structure 10 within the peripheral bonding region of a display includes a substrate 11, a plurality of pads 12 located at the substrate 11 and insulated from each other, a protection layer 13 covering the pads 12 and the substrate 11 and a surface metallic layer 14. The substrate 11 herein has a bonding region 11a and a predetermined-to-be-cut region 11b, and the pads 12 are located within the bonding region 11a. The protection layer 13 has an opening 13a and the opening 13a exposes out parts of the pads 12, so that after entirely removing the partial protection layer 13, and the flexible circuit board (FCB) then can be bonded on the pads 12 exposed by the protection layer 13. For a flexible display, the substrate 11 is spread with a layer of plastic material (not shown) thereon, and during entirely removing a part of the protection layer 13, the etching liquid would erode the plastic material to make the adhesion capability between the plastic material and the substrate 11 poor. As a result, during the successive cutting process (i.e., cutting along the line L-L), peeling phenomena happen. Since the pads are easily affected by erosions of moisture and oxygen, therefore, the regions of the pads 12 exposed out by the protection layer 13 would cover the surface metallic layer 14, in which the region of the surface metallic layer 14 must be greater than the region of each of the pads 12. Since the pads 12 do not extend into the predetermined-to-be-cut region 11b of the substrate 11 and the adhesion capability between the surface metallic layer 14 and the protection layer 13 beneath the surface metallic layer 14 is poor, the breaking off or turning up phenomena of the surface metallic layer 14 during the cutting process (i.e., cutting along the line L-L) easily happen, which further affect the quality of signal transmission.
In order to avoid the breaking off or turning up phenomena of the surface metallic layer 14 due to poor adhesion capability between the surface metallic layer 14 and the protection layer 13 beneath the surface metallic layer 14 during the cutting process (i.e., cutting along the line L-L), a conventional solution is provided, referring to FIG. 5, where the pads 12a of the bonding structure 20 extend from the bonding region 11a into the predetermined-to-be-cut region 11b, so as to make the adhesion capability between the surface metallic layer 14 and the pads 12a beneath the surface metallic layer 14 better. However, the pads 12a in such design would be exposed out after cutting and suffer the erosion of moisture and oxygen, which further makes the frame abnormal when the display receives signals and thus reduces the product reliability.